Method and apparatus for separating lignocellulose particle fraction and lignin particle fraction, lignin particle composition, lignocellulose particle composition and their use

ABSTRACT

The invention relates to a method and an apparatus for separating lignocellulose particle fraction ( 3 ) and lignin particle fraction ( 4 ), in which crude lignin ( 1 ) formed from starting material ( 6 ) comprises lignocellulose particles and lignin particles. According to the invention, the method comprises adding stabilizing chemical ( 11 ) and/or hydrophobic chemical ( 12 ) into the crude lignin ( 1 ) in at least one step, and treating the crude lignin by separating the lignin particle fraction ( 4 ) and lignocellulose particle fraction ( 3 ) from each other in at least one separation step ( 2,8,9,10 ). Further, the invention relates to a lignocellulose particle fraction and a lignin particle fraction and their uses.

FIELD OF THE INVENTION

The invention relates to a method and an apparatus for separatinglignocellulose particle fraction and lignin particle fraction. Further,the invention relates to a lignin particle composition and alignocellulose particle composition and their uses.

BACKGROUND OF THE INVENTION

Known from prior art is different methods for forming lignin fromdifferent raw materials, such as biomass. Many bio-refinery processes,e.g. hydrolysis, generate crude lignin, such as lignin residue, afterhydrolysis of biomass. This water-insoluble lignin residue usuallycontains significant percentage of non-hydrolyzed lignocelluloseparticles together with free lignin particles.

Further, known from prior art is to treat lignin chemically bydissolving lignin in dissolvent, such as in NaOH, alcohol-water mixtureor organic acid, and to precipitate lignin, e.g. by sulphuric acid orwater. Then pure lignin can be provided, but known processes suffer fromhigh operating and capital costs. Removing and/or recovering ofdissolvent or formed salt lead to additional costs. Final dewatering oflignin is usually carried out by filtration. Size of precipitated ligninparticle is generally rather small, which has negative effect onfiltration rate and dry solids content of filter cake.

Objective of the Invention

The objective of the invention is to disclose a new method forseparating lignocellulose particle fraction and lignin particlefraction. Another objective of the invention is to disclose a new methodfor purifying lignin. Another objective of the invention is to produce apurified lignin particle composition and lignocellulose particlecomposition with improved properties.

SUMMARY OF THE INVENTION

The method for separating lignocellulose particle fraction and ligninparticle fraction according to the present invention is characterized bywhat is presented in claim 1.

The apparatus for separating lignocellulose particle fraction and ligninparticle fraction according to the present invention is characterized bywhat is presented in claim 11.

The lignin particle composition according to the present invention ischaracterized by what is presented in claim 16.

The lignocellulose particle composition according to the presentinvention is characterized by what is presented in claim 17.

The use of the lignin particle composition according to the presentinvention is characterized by what is presented in claims 18 and 19.

The use of the lignocellulose particle composition according to thepresent invention is characterized by what is presented in claim 20.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and constitutes a part of thisspecification, illus-trate some embodiments of the invention andtogether with the description help to explain the principles of theinvention. In the drawings:

FIG. 1 is a flow chart illustration of a method according to oneembodiment of the present invention,

FIG. 2 is a flow chart illustration of a method according to anotherembodiment of the present invention,

FIG. 3 is a flow chart illustration of a method according to anotherembodiment of the present invention, and

FIG. 4 is a flow chart illustration of a method according to anotherembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a method for separating lignocellulose particlefraction (3) and lignin particle fraction (4). In the method of thepresent invention crude lignin (1) formed from starting material (6)comprises lignocellulose particles and lignin particles, wherein themethod comprises: adding stabi-lining chemical (11) and/or hydrophobicchemical (12) into the crude lignin (1), such as into the crude ligninor fraction of the crude lignin, in at least one step; and treating thecrude lignin by separating the lignin particle fraction (4) andlignocellulose particle fraction (3) from each other in at least oneseparation step (2,8,9,10). In a preferred embodiment, the ligninparticle fraction is a purified crude lignin.

One embodiment of the method of the present invention is shown inFIG. 1. Another embodiment of the method of the present invention isshown in FIG. 2. Another embodiment of the method of the presentinvention is shown in FIG. 3. Another embodiment of the method of thepresent invention is shown in FIG. 4.

The apparatus of the present invention comprises at least one separatingdevice for separating the lignin particle fraction (4) andlignocellulose particle fraction (3) from each other in at least oneseparation step (2,8,9,10), at least one first feeding device forfeeding the crude lignin (1) into the separating device, and at leastone second feeding device for adding stabilizing chemical (11) and/orhydrophobic chemical (12) into the crude lignin (1), such as into thecrude lignin or fraction of the crude lignin, in at least one step.

The invention is based on a solid-solid separation. Further, theinvention is based on a combination of chemical and mechanical methods.According to the invention, separation of lignocellulose particles fromfree lignin particles is important to increase value of lignincomposition in various applications. Simultaneously the crude lignin,i.e. lignin composition, is purified. According to the invention,lignocellulose composition can be produced. In the present invention thelignocellulose particles may be circulated back to hydrolysis process.

In this context, starting material (6) means any wood or plant based rawmaterial. The starting material includes lignin, lignocellulose andhemicellulose. In one embodiment, the starting material is selected fromthe group consisting of wood based raw material, lignin containingbiomass such as agricultural resi-dues, bagasse and corn stover, woodyperennials, vas-cular plants and their combinations.

In this context, crude lignin (1) refers any material or compositioncontaining lignin particles, such as free lignin particles. Further, thecrude lignin contains also lignocellulose particles. Mainly, the crudelignin comprises cellulose and lignin, but may contain alsohemicelluloses. The crude lignin may contain one or more lignin materialcomponents. The crude lignin may contain different amounts of ligninparticles and lignocellulose particles. Typically, the crude lignin isin the form of suspension which contains water, acid, e.g. formic acid,acetic acid or sulfuric acid, alcohol or other liquid, or in the formcake, lump or the like. In one embodiment, the crude lignin has beendiluted with liquid, e.g. with water, and DS is between 1-20%,preferably between 1-10%. Low consistency of suspension aids mechanicalseparation of free lignin particles and lignocellulose particles. In oneembodiment, weight average particle size of the crude lignin is below1000 μm, preferably below 500 μm.

Preferably, the crude lignin (1) is formed by means of hydrolysis (5).In one embodiment, the hydrolysis is selected from the group consistingof acid hydrolysis, enzymatic hydrolysis, supercritical hydrolysis,subcritical hydrolysis and their combinations. The method of theinvention can be used in connection with any hydrolysis process. In oneembodiment, the crude lignin is a lignin residue from the hydrolysis orcellulignin.

In one embodiment, the cellulose content, i.e. glucan content, of thecrude lignin (1) is 3-70% by weight, preferably 5-60 by weight and morepreferable 10-45% by weight, analyzed as glucose.

In one embodiment, lignocellulose particles (3) are in the form of fibersticks in the crude lignin. In one embodiment, weight average particlesize of the lignocellulose particle is below 1 mm, in one embodimentbelow 0.5 mm and in one embodiment below 300 μm.

The stabilizing chemical (11) and/or hydro-phobic chemical (12) areadded into the crude lignin (1), such as into the crude lignin orfraction of the crude lignin or purified crude lignin, in at least onestep. In one embodiment, the stabilizing chemical (11) and/orhydrophobic chemical (12) are added into the crude lignin (1) in onestep. In one embodiment, the stabilizing chemical (11) and/orhydrophobic chemical (12) are added into the crude lignin or fraction ofthe crude lignin or purified crude lignin in more than one step. In oneembodiment, the stabilizing chemical (11) and/or hydrophobic chemical(12) are added into the crude lignin or fraction of the crude lignin orpurified crude lignin in connection with each separation step. In oneembodiment, the stabilizing chemical (11) and/or hydrophobic chemical(12) are added into the crude lignin or fraction of the crude lignin orpurified crude lignin in the first separation step and/or in at leastone later separation step.

In one embodiment, stabilizing chemical (11) is added into the crudelignin (1), such as into the crude lignin or fraction of the crudelignin or purified crude lignin. In one embodiment, hydrophobic chemical(12) is added into the crude lignin (1), such as into the crude ligninor fraction of the crude lignin or purified crude lignin. In oneembodiment, stabilizing chemical (11) and hydrophobic chemical (12) areadded into the crude lignin (1), such as into the crude lignin orfraction of the crude lignin or purified crude lignin. In oneembodiment, different combinations of stabilizing chemical (11) andhydrophobic chemical (12) may be added in different separation steps. Inone embodiment, the stabilizing and hydro-phobic chemicals are dosedsimultaneously. In one embodiment, the stabilizing and hydrophobicchemicals are dosed sequentially. In one embodiment, the stabilizing andhydrophobic chemicals are added into the crude lignin and the crudelignin is mixed, preferably by high-shear mixing. The chemicals can beadded into slurry of low or high dry solids content. The high-shearmixing is beneficial to facilitate adsorption of chemicals, especiallyhydrophobic chemical, on surfaces. The stabilizing chemicalpredominantly adsorbs on lignocellulose particles, while the hydrophobicchemical predominantly adsorbs on free lignin particles.

In one embodiment, the stabilizing chemical (11) is polysaccharide assuch or modified polysaccharide. In this context, the stabilizingchemical is typically hydrophilic chemical. In one embodiment, thestabilizing chemical is selected from the group consisting ofcarboxymethyl cellulose (CMC), polyanionic cellulose (PAC), othercellulose derivatives, e.g. ethylhydroxyethyl cellulose and methylcellulose, native guar gum, modified guar gum, native starch, modifiedstarch, pectin, glycogen, callose, chrysolaminar in, nativehemicellulose, modified hemicellulose, xylan, mannan, galactomannan,galactoglucomannan (GGM), arabinoxylan, glucuronoxylan and xyloglucan,fucoidan, dextran, alginate, other polysaccharide and theircombinations. Said stabilizing chemical may be in native form or inmodified form. In one embodiment, the stabilizing chemical iscarboxymethyl cellulose (CMC). Preferably, function of the stabilizingchemical is to keep suspended lignocellulose particles stable throughchemical interaction. Therefore, treated lignocellulose particles remainin suspension while free lignin particles are separated from suspension.

In one embodiment, the hydrophobic chemical (12) is selected from thegroup consisting of fuel oil, bio fuel oil, diesel oil, biodiesel oil,naphta, bionaphta, kerosene, biokerosene, other middle distillatefraction, gasoline, biogasoline, naphthalene, bionaphthalene, mineralspirit, other hydrocarbon solvent and their combinations. In oneembodiment, the hydrophobic chemical is oil based chemical or bio-oilbased chemical. In one embodiment, the hydrophobic chemical is selectedfrom the group consisting of diesel oil, biodiesel oil, fuel oil, biofuel oil, kerosene, biokerosene, other middle distillate fraction, andtheir combinations. Preferably, function of the hydrophobic chemical isto cause aggregation of lignin particles together with stabilizingchemical. Increase in particle size of the lignin will help separationby mechanical means. It will also increase hydrophobicity of the ligninparticles thus facilitating dewatering. Need for the hydrophobicchemical is determined by surface properties of free lignin particles,which are largely dependent on physico-chemical conditions in previousprocess stages. The hydrophobic chemical has non-polar nature.

In one embodiment, pH is adjusted in the crude lignin before theseparating. In one embodiment, pH is adjusted to value between 5-7.

In one embodiment, the separation of the lignocellulose particlefraction and lignin particle fraction is carried out in pH range between1-10, preferably between 5-9. Often near neutral pH, such as pH between5-9, stabilizes the lignocellulose particles thus facilitatingseparation. On the other hand, acidic conditions destabilize the ligninparticles improving separation at low pH values.

The separation can be carried out in wide temperature range, e.g.temperatures between 0-100° C. Higher temperature usually aids theseparation due to lower viscosity. Generally near natural processtemperature is utilized to avoid heating or cooling. In one embodiment,the lignin particle fraction (4) and lignocellulose particle fraction(3) are separated from each other by means of a separation methodselected from the group consisting of centrifugal forces, sedimentation,elutriation, aggregation, flotation, flocculation, screening and theircombinations. In one embodiment, the separating is made by means ofcentrifugal forces. In one embodiment, the separating is made by meansof sedimentation. In one embodiment, the separating is made by means ofelutriation. In one embodiment, the separating is made by means ofagglomeration. In one embodiment, the separating is made by means offlocculation. In one embodiment, the separating is made by means offlotation. In one embodiment, the separating is made by means ofscreening. In a preferred embodiment, the lignin particle fraction (4)and lignocellulose particle fraction (3) are separated from each otherso that the lignocellulose particle fraction (3) is separated from thecrude lignin (1) and remaining crude lignin is the lignin particlefraction (4), i.e. the purified crude lignin.

In one embodiment, the apparatus comprises at least two separatingdevice for separating the lignin particle fraction (4) andlignocellulose particle fraction (3) and/or purifying the ligninparticle fraction (4) and/or purifying lignocellulose particle fraction(3). In one embodiment, the separating device is based on centrifugalforces, sedimentation, elutriation, aggregation, flotation,flocculation, screening or their combinations. The separating device maybe reactor, vessel, tank, bowl, cyclone, column, cell, basin, thickeneror the like.

In one embodiment, the lignin particle fraction (4) and lignocelluloseparticle fraction (3) are separated in one separation step (2,8,9,10).In one embodiment, the lignin particle fraction (4) and lignocelluloseparticle fraction (3) are separated in more than one separation step(2,8,9,10).

In one embodiment, the lignin particle fraction (4) and lignocelluloseparticle fraction (3) are separated from each other in the firstseparation step (2). In one embodiment, the first separation step is aninitial separation, such as rougher separation step. The firstseparation step for separating the lignocellulose particle fraction andlignin particle fraction is made by means of centrifugal forces, e.g. bybasket centrifuge or decanter centrifuge such as solid bowl centrifuge,or flotation, e.g. by froth flotation or column flotation. In flotation,stabilized lignocellulose particles remain in suspension while freelignin particles are raised by air bubbles to surface and then eitherscraped or collected as overflow.

In one embodiment, the lignocellulose particle fraction (3) is separatedfrom the lignin particle fraction (4) as a clarifying fraction, e.g. asan overflow of the thickener, in the separation step (2, 8,9,10).

The lignocellulose particle fraction (3) may contain also othercomponents or agents than lignocellulose particles. In one embodiment,the lignocellulose particle fraction (3) is treated, preferably afterthe first separation step (2), by purifying in at least one separationstep (8) which may be selected from the separation methods describedabove. In one embodiment, the lignocellulose particle fraction (3) istreated, preferably purified, in at least one scavenger separation step.In one embodiment, the lignocellulose particle fraction (3) is treatedin two scavenger separation steps. If needed, these purifying steps canbe incorporated to recover remaining lignin particles fromlignocellulose particle fraction.

In one embodiment, the lignocellulose particle fraction (3) is in theform of suspension. This suspension contains liquid, such as water. Inone embodiment, the lignocellulose particle fraction is thickened. Ifneeded, the lignocellulose particle fraction can be thickened by dosingcationic flocculant, e.g. cationic polyacrylamide, followed bycentrifuge, thickener or cyclone. Utilization in other applicationsgenerally involves further dewatering, e.g. by filter or screw press,followed by drying.

In one embodiment, the lignocellulose particle fraction (3) isdewatered, e.g. by a screw press. In one embodiment, the lignocelluloseparticle fraction (3) is ground.

In one embodiment, the lignocellulose particle fraction (3) iscirculated (7) back to manufacturing process of the crude lignin, e.g.to hydrolysis process (5). Alternatively, the lignocellulose particlefraction (3) is circulated to a separate hydrolysis process. Liquid inthe lignocellulose particle fraction replaces partly or totally freshwater needed in dilution of biomass particles prior to hydrolysis. Inone embodiment, the apparatus comprises a circulations means forcirculating (7) the lignocellulose particle fraction (3) back tomanufacturing process of the crude lignin.

In one embodiment, the lignin particle fraction (4) is sediment, sludge,residuum or deposit of the separation step. In one embodiment, thelignin particle fraction (4) is removed as an underflow of separatingdevice, e.g. thickener, in the separation step (2,8,9,10).

The lignin particle fraction (4) may contain also other components oragents than lignin particles. In one embodiment, the lignin particlefraction (4) is treated, preferably after the first separation step (2),by purifying in at least one separation step (9,10) which may beselected from the separation methods described above. In one embodiment,the lignin particle fraction (4) is treated, preferably purified, in atleast one cleaning separation step. In one embodiment, the ligninparticle fraction (4) is treated in two cleaning separation steps. Inone embodiment, the lignin particle fraction is treated in the cleaningseparation step by means of centrifugal cleaning e.g. by hydrocyclone,sedimentation, e.g. by thickener, elutriation, aggregation, flotation,flocculation and/or screening. In one embodiment, the lignin particlefraction is removed from the cleaning separation step as an underflow oras a sediment, sludge, residuum or deposit.

In one embodiment, the lignin particle fraction (4) is washed. Thepurified lignin can be easily neutralized in washing stage withoutnegatively affecting dewatering performance.

One benefit of this kind of separation process is that it toleratespresence of soluble oligomeric sugars in the lignin residue. Typically,if the lignin residue is not carefully washed there are oligomericsugars present, which make filtration extremely complicated due toclogging tendency. In the present invention, the filtration is onlyperformed for the final lignin particle fraction, which is washed and,therefore, contains no oligomeric sugars. Oligomeric sugars may becarried over with the lignocellulose particle fraction back tohydrolysis process. This procedure enables savings in dewatering andwashing of the lignin residue, and also leads to higher sugarconcentration in the hydrolysate. If there is a process without washingthe lignin residue, then present invention demonstrates improved sugaryield.

In one embodiment, the lignin particle fraction (4) is filtrated, e.g.by a pressure filter. In one embodiment, the lignin particle fraction(4) is dewatered. In one embodiment, the lignin particle fraction (4) istreated by grinding.

In one embodiment, the apparatus comprises at least one dewateringdevice for dewatering the lignin particle fraction (4) or thelignocellulose particle fraction (3).

Improvement in dewatering of the lignin is important for the presentinvention. Removal of the lignocellulose particles clearly improvesdewatering of the lignin. This means that less energy is needed indrying, and often investment in dryer can be neglected totally, if thepurified lignin is burnt or used in applications not requiring lowmoisture content. Size of free lignin particles after hydrolysis isgenerally big, e.g. d50 over 10 μm, as compared to precipitated ligninparticle meaning higher filtration rate and dry solids content of filtercake.

The process of the present invention minimizes waste water and oftentotally closed loop can be achieved. Clean water is added only in afinal stage of the lignin purification. With suitable consistency of thelignocellulose particle fraction incoming and outgoing flows are inbalance without additional flow to waste water treatment plant. Thelignin is not dis-solved in any stage preventing formation of lowmolecular weight phenolic compounds, which would otherwise complicatescirculation or disposal of filtrates and overflows.

According to present invention a lignin particle composition can beformed. The lignin particle composition includes lignin particlefraction of the crude lignin in which the crude lignin has been formedfrom starting material and the crude lignin comprises lignocelluloseparticles and lignin particles, and the lignin particle fraction hasbeen formed from the crude lignin by adding stabilizing chemical and/orhydrophobic chemical into the crude lignin, and by separating thelignocellulose particle fraction from the lignin particle fraction in atleast one separation step. The lignin particle composition may be usedas component in manufacturing a final product selected from the groupconsisting of activated carbon, carbon fiber, lignin composite, bindermaterial, resins, phenolic component and/or dispersion agent. In oneembodiment, the lignin particle composition is used as an ad-sorbent foroil or heavy metals. In one embodiment, the lignin particle compositionis used as combustible matter in energy production.

According to present invention a lignocellulose particle composition canbe formed. The lignocellulose particle composition includeslignocellulose particle fraction of the crude lignin in which the crudelignin has been formed from starting material and the crude lignincomprises lignocellulose particles and lignin particles, and thelignocellulose particle fraction has been formed from the crude ligninby adding stabilizing chemical and/or hydrophobic chemical into thecrude lignin, and by separating the lignocellulose particle fractionfrom the lignin particle fraction in at least one separation step. Thelignocellulose particle composition may be used as component inmanufacturing a product selected from the group consisting ofcomposites, wood composites, wood-plastic composites comprisingcomposites formed from plastic, synthetic polymers, biopolymers, rubberor their combinations together with wood, resins, preferably as fillerin resins, wood based materials, wood based fillers, constructionmaterials, building boards, glue boards and/or other wood based boards,such as a particle board, an oriented strand board, a chip board, anintrallam, a gluelam, a hardboard, a waferboard, a fiber board or aplywood. In one embodiment, the lignocellulose particle composition isused as combustible matter in energy production.

The method according to the present invention provides the ligninparticle composition and the lignocellulose particle composition withgood quality. When improving the purify and increasing dry solidscontent of the lignin and lignocellulose compositions so then it may beprovided better properties of the final product. Thanks to theinvention, preferably improved filterability is achieved. Further, bymeans of the invention dewatering can be improved. Preferably, treatingcosts of the lignin can be decreased. Further, thanks to the inventionheat value of the lignin and lignocellulose compositions can beincreased so that the heat value without drying may even at least beduplicated.

The present invention provides an industrially applicable, simple andaffordable way of making the purified lignin based composition andlignocellulose composition from the starting material. The methodaccording to the present invention is easy and simple to realize as aproduction process. The method according to the present invention issuitable for use in the manufacture of the different lignin andlignocellulose based products and final products from different startingmaterials. In one embodiment, the crude lignin is purified from thelignocellulose particles. Further, the lignin and lignocellulosecompositions can be used as sources of energy.

EXAMPLES

The invention is described in more detail by the following examples withreference to accompanying drawings.

Example 1

In this example a lignocellulose particle fraction (3) and ligninparticle fraction (4) are separated according to a process of FIG. 1.

The crude lignin (1) is formed from starting material (6) compriseslignocellulose particles and lignin particles by means of hydrolysis(5). The crude lignin (1) is fed into the separation step (2) whereinstabilizing chemical (11) and/or hydrophobic chemical (12) are fed intothe crude lignin (1). The lignocellulose particle fraction (3) isseparated from the crude lignin so that remaining crude lignin is thelignin particle fraction (4), i.e. the purified crude lignin.Alternatively, the lignocellulose particle fraction (3) may becirculated back to the manufacture of the crude lignin.

Example 2

In this example a lignocellulose particle fraction (3) and ligninparticle fraction (4) are separated according to a process of FIG. 2.

The crude lignin (1) is formed from starting material (6) compriseslignocellulose particles and lignin particles by means of hydrolysis(5). The crude lignin (1) is fed into the first separation step (2)wherein stabilizing chemical (11) and/or hydrophobic chemical (12) arefed into the crude lignin (1). The lignocellulose particle fraction (3)is separated from the crude lignin, and the separated lignocelluloseparticle fraction (3) is purified in the additional separation step (8).Stabilizing chemical (11) and/or hydrophobic chemical (12) may be addedin the additional separation step (8). The remaining crude ligninresiduum is purified in the additional separation step (9) in order toform the lignin particle fraction (4), i.e. the purified crude lignin.Stabilizing chemical (11) and/or hydrophobic chemical (12) may be addedin the additional separation step (9). In an alternative embodiment, thestabilizing chemical (11) and/or hydrophobic chemical (12) are addedonly into the fraction of the crude lignin, such as the lignocelluloseparticle fraction and/or remaining crude lignin residuum, in theadditional separation step (8) and/or additional separation step (9)after the first separation step (2).

Alternatively, the lignocellulose particle fraction (3) may becirculated back to the manufacture of the crude lignin.

Example 3

In this example a lignocellulose particle fraction (3) and ligninparticle fraction (4) are separated according to a process of FIG. 3.

The crude lignin (1) is formed from starting material (6) compriseslignocellulose particles and lignin particles by means of hydrolysis(5). The crude lignin (1) is fed into the first separation step (2)wherein stabilizing chemical (11) and/or hydrophobic chemical (12) arefed into the crude lignin (1). The lignocellulose particle fraction (3)is separated from the crude lignin. The remaining crude lignin residuumis purified in the second (9) and third (10) separation steps in orderto form the lignin particle fraction (4), i.e. the purified crudelignin. Stabilizing chemical (11) and/or hydrophobic chemical (12) maybe added in the second (9) and/or third (10) separation steps.Alternatively, the lignocellulose particle fraction (3) may becirculated back to the manufacture of the crude lignin.

Example 4

In this example, lignin (4) was purified and lignocellulose (3) wasseparated from the crude lignin (1) according to FIG. 4.

The crude lignin (1) analyzed to contain 63.3% acid-insoluble lignin,3.4% acid-soluble lignin, 35.8% glucose and 36.3% total carbohydrateswas re-slurried with water (14). Slurry was diluted (13) to 4% drysolids content and pH was 3.7. Carboxymethyl cellulose (CMC) (11) wasadded 3.5 kg/t ds and kerosene (12) was added simultaneously 4.5 kg/t dsfollowed by high-shear mixing for 3 min. Rougher purification wasperformed using Alfa Laval LAPX 404 separator (basket centrifuge) byfeed rate of 15 l/min at 50° C. temperature in the first separation step(2). After rougher stage sediment contained 88.2% acid-insoluble lignin,2.6% acid-soluble lignin and 8.3% glucose. Lighter solid phase, i.e.lignocellulose fraction (3), contained only 25.1% acid-insoluble ligninand 2.0% acid-soluble lignin referring to efficient solid-solidseparation. Great majority of lignin present in lighter solid phase isbound into lignocellulose particles.

The collected pre-cleaned lignin (15) was further cleaned in two stages(9,10) utilizing sedimentation. Slurry was diluted to 5% dry solidscontent with clean water (18). CMC (11) was added 1.0 kg/t ds andkerosene (12) was added simultaneously 1.4 kg/t ds followed byhigh-shear mixing for 3 min. 800 ml of slurry was sedimented for 10 minat 40′C temperature. Surprisingly, black lignin particles rapidlysettled, while brown lignocellulose particles remained in suspension.Overflow (16) was decanted away and black high-consistency (ds 50%)underflow (17) was further cleaned in the third stage (10) in similarmanner than in the second stage (9) except that CMC (11) was now dosed0.5 kg/t ds and kerosene (12) was dosed 0.7 kg/t ds. Surprisingly, itwas observed that the separation of the lignin particles andlignocellulose particles can be made successfully though there is onlysmall difference in density and size of said particles.

After purification lignin product (4) con-taming 94.3% acid-insolublelignin, 3.2% acid-soluble lignin and 2.7% glucose was recovered.

Example 5

In this example, lignin (4) was purified and lignocellulose (3) wasseparated from the crude lignin (1) according to a process of FIG. 4.

The crude lignin (1) contained 97% particles smaller than 100 μm asmeasured by screening. Median particle size was 20 μm measured byCoulter LS laser diffraction analyzer.

The crude lignin (1) analyzed to contain 68.0% acid-insoluble lignin,1.9% acid-soluble lignin, 31.3% glucose and 31.8% total carbohydrateswas re-slurried with water (14). Slurry was diluted (13) to 3.5% drysolids content and pH was adjusted to 6.5 with NaOH. Carboxymethylcellulose (CMC) (11) was added 4.5 kg/t ds followed by high-shear mixingfor 3 min. Rougher purification was performed using Alfa Laval LAPX 404separator (basket centrifuge) by feed rate of 15 l/min at 52° C.temperature in the first separation step (2). After rougher stagesediment contained 85.1% acid-insoluble lignin, 1.8% acid-soluble ligninand 12.7% glucose.

The collected pre-cleaned lignin (15) was further cleaned in two stages(9,10) utilizing sedimentation. Slurry was diluted to 5% dry solidscontent with clean water (18). CMC (11) was added 1.0 kg/t ds followedby high-shear mixing for 3 min. 800 ml of slurry was sedimented for 10min at 50° C. temperature. Black lignin particles rapidly settled, whilebrown lignocellulose particles remained in suspension. Overflow (16) wasdecanted away and black high-consistency underflow (17) was furthercleaned in the third stage (10) in similar manner than in the secondstage (9) except that CMC (11) was now dosed 0.5 kg/t ds.

After purification lignin product (4) containing 89.7% acid-insolublelignin, 1.4% acid-soluble lignin and 6.1% glucose was recovered. In thecleaning stages recovery of underflow solids was 50% of total solids.

As reference, test was repeated for crude lignin (1) without addition ofCMC (11) and without pH adjustment. After rougher stage (2) sedimentcontained 82.0% acid-insoluble lignin, 1.8% acid-soluble lignin and17.8% glucose. During cleaning stages (9, 10) no aggregation or fastsettling of free lignin particles was noticed. Additionally,lignocellulose particles started to destabilize, i.e. to settle. Similarmass of wet underflow was collected as in test applying CMC. Afterpurification lignin product (4) containing 85.6% acid-insoluble lignin,1.6% acid-soluble lignin and 10.7% glucose was recovered. In thecleaning stages recovery of underflow solids was only 8% of totalsolids.

The results show that applying CMC as stabilizing agent clearly improvesselectivity of mechanical solid-solid separation as compared tosituation without any chemicals.

Example 6

In this example, the purified lignin product (4) formed according toExample 3 was filtrated.

The purified crude lignin slurry (4) at pH 7.0 was filtrated usinghorizontal 0.1 m² plate pressure filter. As reference crude ligninwithout purification was also filtrated. The crude lignin in 40% drysolids content was re-slurried with clean water to 14.4% ds beforefiltration, pH of filtrated slurry was 3.4. In both cases compressionstage was ended when filtrate flow lowered to 15 ml/kg ds cake/min.Filtration temperature was 60-70° C. Results are shown in Table 1.

TABLE 1 Dry solids content Filtration rate Sample of filter cake (%) (kgds/m²/h) Crude lignin 48.4 1.3 Purified lignin 81.3 564 Purified lignin83.2 455

Filtration rate was calculated based on combination of feed, compressionand air blow (30 s) stages. Technical time was not taken into account.Huge difference in filtration rates between the purified and crudelignins is mostly caused by variation in compression time. For thepurified lignin 2-3 min at 15 bar was enough, whereas 150 min at 15 barwas needed for the crude lignin. Also amount of lignin filtrated percycle is significantly higher for the purified lignin. Exceptionallyhigh dry solids content for the purified lignin cake was demonstratedtogether with high filtration rate in neutral conditions.

The method according to the present invention is suitable in differentembodiments to be used for separating the most different kinds oflignocellulose particles from lignin particles.

The invention is not limited merely to the example referred to above;instead many variations are possible within the scope of the inventiveidea de-fined by the claims.

1. A method for separating a lignocellulose particle fraction and alignin particle fraction from crude lignin, the method comprising:adding a stabilizing chemical and, optionally, a hydrophobic chemicalinto the crude lignin in at least one step, wherein the crude lignin isformed from a wood or plant-based raw material, and separating thelignin particle fraction and the lignocellulose particle fraction fromthe crude lignin in more than one solid-solid separation step. 2.(canceled)
 3. The method according to claim 1 wherein the at least onesolid-solid separation step includes application of centrifugal forces,sedimentation, elutriation, aggregation, flotation, flocculation,screening, or any combination thereof.
 4. The method according to claim1, wherein the crude lignin is formed by hydrolysis.
 5. The methodaccording to claim 1, wherein the stabilizing chemical ispolysaccharide.
 6. The method according to claim 1, wherein thehydrophobic chemical includes diesel oil, biodiesel oil, fuel oil, biofuel oil, kerosene, biokerosene, other middle distillate fraction, orany combination thereof.
 7. The method according to claim 2, wherein thelignin particle fraction and lignocellulose particle fraction areseparated from each other in the first separation step.
 8. The methodaccording to claim 1, further comprising purifying the lignocelluloseparticle fraction in at least one purification step.
 9. The methodaccording to claim 1, further comprising purifying the lignin particlefraction in at least one purification step.
 10. The method according toclaim 1 further comprising: forming the crude lignin from a startingmaterial; and circulating the lignocellulose particle fraction such thatthe lignocellulose particle fraction is combined with the startingmaterial to form additional crude lignin.
 11. An apparatus forseparating a lignocellulose particle fraction and a lignin particlefraction from crude lignin, the apparatus comprising: at least twosolid-solid separating devices for separating the lignin particlefraction and the lignocellulose particle fraction from the crude ligninin more than one solid-solid separation step, wherein the crude ligninis formed from a wood or plant-based raw material; at least one firstfeeding device for feeding the crude lignin into the at least onesolid-solid separating device; and at least one second feeding devicefor adding a stabilizing chemical and, optionally, a hydro-phobicchemical into the crude lignin in at least one step.
 12. (canceled) 13.The apparatus according to claim 11, wherein the at least onesolid-solid separating device is configured to apply centrifugal forces,sedimentation, elutriation, aggregation, flotation, flocculation,screening, or any combination thereof.
 14. The apparatus according toclaim 11, further comprising: a circulations means for circulating thelignocellulose particle fraction to combine it with starting materialused to form the crude lignin.
 15. The apparatus according to claim 11,wherein the apparatus comprises at least one dewatering device fordewatering the lignin particle fraction or the lignocellulose particlefraction.
 16. A lignin particle composition, comprising: a ligninparticle fraction of crude lignin and the crude lignin comprisinglignocellulose particles and lignin particles, wherein the ligninparticle fraction has been formed from the crude lignin by addingstabilizing chemical and, optionally, hydrophobic chemical into thecrude lignin in at least one step, wherein the crude lignin is formedfrom a wood or plant-based raw material, and by separating thelignocellulose particle fraction from the lignin particle fraction inmore than one solid-solid separation step.
 17. A lignocellulose particlecomposition comprising: a lignocellulose particle fraction of crudelignin, the crude lignin comprising lignocellulose particles and ligninparticles, wherein the lignocellulose particle fraction has been formedfrom the crude lignin by adding stabilizing chemical and, optionally,hydrophobic chemical into the crude lignin in at least one step, whereinthe crude lignin is formed from a wood or plant-based raw material, andby separating the lignin particle fraction from the lignocelluloseparticle fraction in more than one solid-solid separation step. 18-20.(canceled)